Electron discharge device



y 2, 1935. w. L. PARROTT 2,006,560

ELECTRON DISCHARGE DEVICE Filed Jan. 28, 1930 INVENTOR WL. PflRRorr.

ATTORN Y Patented July 2, 1935 ELECTRON DISCHARGE DEVICE Warley L.Parrott, East Orange, N. L, assignor to Westinghouse Lamp Company, acorporation of Pennsylvania Application January 28, 1930, Serial No.423,934

3Claims.

This invention relates to electron discharge devices and moreparticularly relates to electron discharge devices incorporating anelectron emitting hot cathode of the indirectly heated type,

5 the heater element of which is energized by the passage of analternating electric current therethrough, and is more particularly animprovement in the invention set forth in copending applications SerialNo. 292,116 filed July 12, 1928 and 372,331 filed June 20, 1929 by JohnW. Marden'and Ernst Anton Lederer, and application Serial No. 402,559filed October 20, 1929 by Warley L. Parrott which applications areassigned to the same assignee as the present invention. The Warley L.Parrott of the above identified copending application is the same WarleyL. Parrott of the present invention.

In copending applications Serial No. 292,116 and 372,331 is disclosed anelectron discharge device comprised of an enclosing glass envelope,

an electron emitting cathode of the indirectly heated type, at least oneconcentrically disposed cooperating electrode, said cathode beingcomprised substantially ofa tubular metal sleeve member exteriorlycoated with electron emitting material, refractory insulating end plugmembers, lead wires extending through the end plug members, and aninteriorly disposed coil type heater-element electrically connected tothe lead wires. To prevent deleterious electrical discharges from thelead wires to the cooperating electrodes of the device when the heaterelement is energized by alternating electric current a. dielectricshield member is interposed between the lead wires and the cooperatingelectrode; to eliminate deleterious electrical effects caused bythermionic electron emission from the incandescent heater element, theheater element is designed to operate at a temperature substantiallybelow the temperature of active electron emission.

In copending application Serial No. 402,559 by Warley L. Parrott isdisclosed an improvement over the two first identified Marden andLederer applications, wherein the coil type heater element of the Mardenand Lederer applications is replaced by a non-inductively wound coiltype heater element, whereby a substantial elimination of thedeleterious electrical efiectscaused by the induced electrical currentsin the heretofore employed coil type filaments resulting in the socalledhum characteristic of the device is substantially eliminated, and arelatively closer and more accurate spacing of the elements of thedevice is thereby-obtained. The features of the prior art device of the.Marden and Lederer applications Serial No. 292,116 and Serial No.372,331 of electrically shielding the lead wires of the heater elementfrom the cooperating electrodes and of operating the heater element at atemperature substantially below the temperature of active electronemission are substantially retained in this copending Parrottapplication above identified.

It is one of the objects of the present invention tate the mounting ofthe elements in an elec- 15.

tron discharge device incorporating an electron emitting cathode of theindirectly heated type.

Another object of this invention is to improve and facilitate themanufacture of such devices.

Another object of this invention'isto provide an electron dischargedevice employing an electron emitting cathode of the indirectly heatedtype, the heater element of which is to be energized by alternatingelectric current, which device may be rapidly assembled and manufacturedby modern radio tube machine assembly and manufacturing methods.

Other objects and advantages will become apparent as the invention ismore fully disclosed.

In accordance with the above objects I have found that the dielectricshield member and the cathode sleeve end plug members of the aboveidentified Marden and Lederer copending applications may be entirelydispensed with and that a small compact simplified assembly of elementssupported on lead wires extending from a common stem provided, which maybe rapidly and accurately assembled, and 'the device thus assembled maybe subsequently put through the high speed mechanical manufacturingoperationsof modern radio tube assembly with high manufacturingefliciency.

Before further disclosing the nature of my invention reference should behad to the accompanying drawing wherein,

Fig. 1 illustrates in enlarged detail a non-inductively wound cathodeheater element, such as is set forth and claimed in copendingapplication Serial No. 402,559 above identified;

Fig. 2 is a view partly in cross-section of an electrode assembly of anelectron discharge device mounted in accordance with the presentinvention;

Fig. 3 is a top view of the electrode assembly illustrating one featureof the present invention: and

Fig. 4 is a side elevational view of an electron discharge device withthe enclosing glass envelope broken away to show the assembly of elementherein.

Referring to Fig. 1 the non-inductively wound cathode heater element iscomprised of a noninductive coil type filamentary conductor I, comprisedof a refractory metal such as tungsten, and a refractory core member 2which is comprised substantially of electrically insulating materialsuch as aluminium oxide, magnesium silicate, magnesium oxide and thelike refractory materials, the exterior surface of the assembly beingcoated with refractory electrically insulating material 3, in accordancewith the practice set forth in my copending application Serial No.402,559 above identified.

The process of assembling this heater unit briefly stated comprisesfirst shaping the twin coil heater element about a mandrel of thedesired diameter replacing the mandrel with the refractory core member,annealing the shaped twin coil helix in hydrogen to about 1400 C. to setthe coil turns on the core member, exteriorly coating the assembly withrefractory insulating materials such as aluminium oxide, talc, magnesiumsilicate, and the like which are non-deleterious with respect to theheater element wire and again baking the assembly to consolidate andcement the exterior coating of refractory material to the surface of thecoiled heater member I and to the refractory core member 2.

By the practice of this invention a rigid cathode heater assembly isobtained wnich is substantially self supporting when terminals 4 and 5are electrically connected, as by spot welding to leading in supportwires Ii and 1 in Fig. 2.

In accordance with the present invention this cathode heater assembly isfirst inserted in a metal tubular sleeve member 8 having a diameterslightly greater than the overall diameter of the heater assembly, and alength appreciably greater than the overall length of the same, theexterior surface of the sleeve member having been previously coated inany desirable manner at least in part with thermionically activematerial such as admixtures of alkaline earth metal compounds which maybe thermally decomposed into alkaline earth metal oxides when desired.

The terminals 4 and 5 of the heater element 1 are then electricallyunited to the leading-in support wires 6 and I (Fig. 2) of the mountassembly of the electrical device incorporating the same.

The mount assembly typical of the present invention is shown in Fig. 2and is substantially that which is employed in radio receiving tubesknown in the trade as UY 227 tube. This type tube comprises essentiallyin a centrally disposed electron emitting cathode of the indirectlyheated type the heater element of which is energized by alternatingelectric current, such as is shown in Fig. 1, and concentricallyarranged control and anode electrodes, the latter of which is preferablycomprised of perforated or meshed metal materials which have high heatradiating and low heat reflecting capacities, for the purpose ofpreventing the heating up of the internally situated grid or controlelectrode to such temperatures at which the electrode itself would tendto emit thermionic electron emission.

The method of mounting the electrodes in accordance with the practice ofthe present invention is substantially as follows: The non-inductiveheater element prepared in accordance with the teachings of UnitedStates Patents No. 1,865,422 issued July 5, 1932 and No. 1,972,162issued September 4, 1934, is first mounted in the usual manner on thefilament lead wires 5 and I. The cathode sleeve member is then placed inposition therearound and electrically connected by means of metal strip28 to lead wire 29.

The grid (I1) and anode (I6) electrodes are next placed in position andelectrically united to support wires 9 and III as by welding thereto. Anelectrically insulating spacer member 22 which may be comprised in thepresent example of sheet mica of approximately 10 m.m. width by 20 mm.length, having five properly spaced holes is then threaded down over theend of the two main support wires 9 and III, the grid posts l8 and I9and the cathode sleeve member 8, in a manner as indicated in Fig. 2.

The mica spacer member is shown in more particularity in Fig. 3, whichis a top view looking down on the spacer member in position as in Fig.

2. It is preferable to rigidly engage the spacer member to support wires9 and In which is accomplished in the present illustration by means ofeyelets 23 and 24 the collar of which eyelet is integral with the spacermember 22 and the sleeve of which is rigidly united to the support wires9 and ID in any convenient manner as by frictional engagement or by spotwelding the sleeve thereto. 30

The final stp of the mounting operation consists in the closing up orpinching together of the open end of the cathode sleeve member 8projecting above the spacer member 22 through the central opening 25 inthe manner shown in Fig. 3. This pinching together serves a two foldpurpose, first in serving to position the sleeve member in the assemblyand restrain the same from relative displacement and secondly, theclosure of the end of the sleeve member substantially prevents theescape of heat energy and prevents deleterious electrical discharge fromthe incandescent alternating current energized heater element and thecooperating electrodes of the device as a result of the differences orvariations in electrical potentials therebetween.

In accordance with the teachings of copend ing application Serial No.372,331, the operating temperature of the heater element is maintainedsubstantially below the temperature of active thermionic emission eitherfrom the heater element wire itself or from the associated refractoryinsulating materials.

The remaining elements of the device are substantially as heretoforedisclosed by the art in that the lead support wires 6, I, 9, l0 and 29are electrically connected through press II to exterior electricalconductors 25, 21, l2, l3 and 30 in the usual manner by dumet seals l4.Means are provided for cleaning up residual gases such as by getter l5,mounted on getter helmet 2i and supported by means of support wire 20integral with main support wire ill in a position such that thevaporized getter material does not deposit across press II to causedeleterious electrical leakage.

The compact completed assembly comprising the enclosing glass envelope3|, a base member 32, the cathode, cooperating electrodes, and the likeelements of the device may be noted in Fig. 4 wherein a 227 type tubeconstructed in accordance with the present invention is shown. Theenclosing glass envelope is broken away.

It may be noted that the compactness and simplicity of the assembly ascompared to prior with electron emitting material and an interiorly'devices is marked. This results in minimum costs of production with amaximum conservation of time and labor. The device may be readilymanufactured by high speed sealing in and exhaust methods and theresultant manufacturing efficiency is relatively high.

A 227 receiving tube device constructed in accordance with the presentinvention eliminating the dielectric shield members and the cathode endplug members of the prior devices, has a hum value resulting fromdeleterious electrical leakages of less than one millivolt as comparedto Z to 3 millivolts of the prior art devices, and a maximum heating uptime of cathode not to exceed substantially 7 to 8 seconds as comparedto 14 to 20 seconds of the prior artdevices. Moreover the method ofrigid assembly and positioning of elements results in a substantially11onmicrophonic structure, and a device having highly uniform electricalcharacteristics.

Having broadly and specifically disclosed the nature of my invention itis apparent that there may be many variations and departures made of thespecific embodiment herein disclosed, and such variations and departuresare anticipated as may fall within the scope of the following claims.

What is claimed is:

1. An electron discharge device comprising an enclosing glass envelope,cathode, grid and anode electrodes supported from a common press andmaintained in spaced relationship by means of a spacer member secured tothe support wires of said press, lead Wires extending through said pressand electrically connected to said electrodes, said anode electrodecomprising a meshed plate material of relatively high heat radiatingcapacity and relatively low heat reflecting capacity', and said cathodeelectrode comprising a tubular metal sleeve member exteriorly coatedpositioned non-inductively wound coil type heater element having theterminals extending from one end thereof, said sleeve member beingsubstantially sealed at the end remote from the common press of thedevice and supported thereby by means of said spacer member secured tothe support wires of the said common press.

2. In an electron discharge device the combination of an electronemitting cathode of the indirectly heated type, the heater element ofwhich. is energized by the passage of an electric current therethrough,a meshed plate anode electrode and a control electrode, supported from acommon press concentric to said cathode electrode, the heater element ofsaid cathode being comprised of a substantially noninductive coil typerefractory metal filament operating at a temperature substantially belowthe temperature of active electron emission, the terminals of said coilextending from one end thereof, an electrically insulating spacermember, and the electron emitting element of said cathode beingcomprised of a tubular metal sleeve member substantially closed at oneend and supported thereby by means of said electrically insulatingspacer member fixed in position with respect to said anode and controlelectrodes at a point remote from the common press of the device.

3. A radio tube includingan anode plate, a grid, a tubular cathodeelement, together with an insulating plate at the top of said anodeplate positively engaging all three elements to maintain them in properspaced relation with respect to each other, the tubular cathode elementpassing through an opening in the top insulating plate and having aprojecting end crimped to anchor it to said insulating plate.

"WARLEY L.

